do-offscreen combinator for managing resources while running a gadget offscreen. tweak bgr[a]>bitmap to copy the pixel memory

extra/graphics/bitmap/bitmap.factor

@@ -4,32 +4,35 @@
 USING: alien arrays byte-arrays combinators summary io.backend
 graphics.viewer io io.binary io.files kernel libc math
 math.functions math.bitwise namespaces opengl opengl.gl
-prettyprint sequences strings ui ui.gadgets.panes
-io.encodings.binary accessors grouping ;
+prettyprint sequences strings ui ui.gadgets.panes fry
+io.encodings.binary accessors grouping macros alien.c-types ;
 IN: graphics.bitmap
 
-! Currently can only handle 24bit bitmaps.
+! Currently can only handle 24/32bit bitmaps.
 ! Handles row-reversed bitmaps (their height is negative)
 
 TUPLE: bitmap magic size reserved offset header-length width
     height planes bit-count compression size-image
     x-pels y-pels color-used color-important rgb-quads color-index array ;
 
+: (array-copy) ( bitmap array -- bitmap array' )
+    over size-image>> abs memory>byte-array ;
+
+MACRO: (nbits>bitmap) ( bits -- )
+    [ -3 shift ] keep '[
+        bitmap new
+            2over * _ * >>size-image
+            swap >>height
+            swap >>width
+            swap (array-copy) [ >>array ] [ >>color-index ] bi
+            _ >>bit-count
+    ] ;
+
 : bgr>bitmap ( array height width -- bitmap )
-    bitmap new
-        2over * 3 * >>size-image
-        swap >>height
-        swap >>width
-        swap [ >>array ] [ >>color-index ] bi
-        24 >>bit-count ;
+    24 (nbits>bitmap) ;
 
 : bgra>bitmap ( array height width -- bitmap )
-    bitmap new
-        2over * 4 * >>size-image
-        swap >>height
-        swap >>width
-        swap [ >>array ] [ >>color-index ] bi
-        32 >>bit-count ;
+    32 (nbits>bitmap) ;
 
 : 8bit>array ( bitmap -- array )
     [ rgb-quads>> 4 <sliced-groups> [ 3 head-slice ] map ]

extra/ui/offscreen/offscreen.factor

@@ -1,5 +1,5 @@
-USING: accessors graphics.bitmap kernel math sequences
-ui.gadgets ui.gadgets.worlds ui ui.backend ;
+USING: accessors continuations graphics.bitmap kernel math
+sequences ui.gadgets ui.gadgets.worlds ui ui.backend ;
 IN: ui.offscreen
 
 TUPLE: offscreen-world < world ;
@@ -16,9 +16,16 @@ M: offscreen-world ungraft*
     [ reset-world ] tri ;
 
 : open-offscreen ( gadget -- world )
-    "" f <offscreen-world> [ open-world-window ] keep ;
+    "" f <offscreen-world> [ open-world-window ] keep
+    notify-queued ;
+
+: close-offscreen ( world -- )
+    ungraft notify-queued ;
 
 : offscreen-world>bitmap ( world -- bitmap )
     [ handle>> offscreen-pixels ] [ dim>> first2 neg ] bi
     bgra>bitmap ;
     
+: do-offscreen ( gadget quot: ( offscreen-world -- ) -- )
+    [ open-offscreen ] dip
+    over [ slip ] [ close-offscreen ] [ ] cleanup ;